The role of fullerene derivatives in perovskite solar cells: electron transporting or electron extraction layers?
- 15 February 2021
- journal article
- research article
- Published by Royal Society of Chemistry (RSC) in Journal of Materials Chemistry C
- Vol. 9 (33), 10759-10767
- https://doi.org/10.1039/d0tc05903j
Abstract
The synthesis, characterization and incorporation of fullerene derivatives bearing primary, secondary and tertiary nitrogen atoms, which possess different basicities, in perovskite solar cells (PSCs), is reported. In this work, we tested the compounds as conventional electron transporting materials (ETMs) in a single layer with phenyl-C61-butyric acid methyl ester (PC61BM) as control. Additionally, we tested the idea of separating the ETM into two different layers: a thin electron extracting layer (EEL) at the interface with the perovskite, and an electron transporting layer (ETL) to transport the electrons to the Ag electrode. The compounds in this work were also tested as EELs with C60 as ETL on top. Our results show that the new fullerenes perform better as EELs than as ETMs. A maximum power conversion efficiency (PCE) value of 18.88% was obtained for a device where a thin layer (~3 nm) of BPy-C60 was used as EEL, a higher value than that of the control device (16.70%) with only pure C60. Increasing the layer thicknesses led to dramatically decreased PCE values, clearly proving that the compound is an excellent electron extractor from the perovskite layer but a poor transporter as a bulk material. The improved passivation ability and electron extraction capabilities of the BPy-C60 derivative were demonstrated by steady-state and time-resolved photoluminescence (SS-and TRPL) as well as electrochemical impedance spectroscopy (EIS) and X-Ray photoelectron spectroscopy (XPS) measurements; likely attributed to the enhanced basicity of the pyridine groups that contributes to a stronger interaction with the interfacial Pb2+ .Funding Information
- National Science Foundation (CHE-1801317)
- Welch Foundation (AH-0033)
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